Intermittent upload error: 412: The server does not meet one of the preconditions of the requester

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Steps to reproduce

1. Intermittent problem that occurs when manually or auto-uploading files to nextcloud from ios app

Expected behaviour

The error should either not occur or should be more specific as to what the problem is and how to resolve it

Actual behaviour

When uploading files, either through automatic photos upload, or manually uploading files, there sometimes occurs errors that show "412: The server does not meet one of the preconditions of the requester".
These seem to be retried at least some of the time, and eventually seem to either be uploaded successfully or just disappear from the list of files to be uploaded.

Logs

If applicable, you can post the iOS app or server logs (removing any sensitive information).

Reasoning or why should it be changed/implemented?

Environment data

iOS version: iOS 26.4.2

Nextcloud iOS app version: 33.0.8.1

Server operating system: Debian trixie amd64

Web server: Apache

Database: MariaDB 11.8.6

PHP version: 8.4.21

Nextcloud version: 31.0.12

Start with the iOS app's automatic photo-upload and manual file-upload entry points, then reproduce the intermittent 412 response while collecting the app and server logs requested in the issue. Compare cases that eventually upload with cases that disappear, and document a reliable cause or a more specific user-facing error.